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Carbon emissions dissolve the seabed, especially in the North Atlantic Ocean. Shown here, Azkorri Beach in the Basque Country in northern Spain.
Credit: Inaki Bolumburu / Shutterstock
Climate change is spreading to the bottom of the sea.
The same greenhouse gas emissions that cause the changing climate of the planet also result in the dissolution of the seabed. And new research has shown that the bottom of the ocean melted faster in some places than in others.
The ocean is what is called a carbon sink: it absorbs carbon from the atmosphere. And this carbon acidifies the water. In the oceanic depths, where pressure is high, this acidified seawater reacts with calcium carbonate from dead-shell creatures. The reaction neutralizes the carbon, creating bicarbonate.
Over the millennia, this reaction has been a convenient way to store carbon without completely destroying the chemistry of the ocean. But as humans have burned fossil fuels, more and more carbon has been found in the ocean. In fact, according to NASA, about 48% of the excess carbon that humans injected into the atmosphere has been trapped in the oceans. [7 Ways the Earth Changes in the Blink of an Eye]
All this carbon means more acidic oceans, which means faster dissolution of calcium carbonate on the seabed. To determine how quickly mankind burns the supply of calcium carbonate from the ocean floor, researchers at Princeton University's atmosphere and ocean scientist, Robert Key, estimated the rate of Probably worldwide dissolution using streamflow data, calcium carbonate measurements in the sediments of key indicator bottoms such as ocean salinity and temperature. They compared this rate with that before the industrial revolution.
Their results, published October 29 in the journal Proceedings of the National Academy of Sciences, combine good and bad news. The good news is that most areas of the oceans have not yet shown a dramatic difference in the rate of calcium carbonate dissolution before and after the industrial revolution. However, there are many hot spots where human-made carbon emissions make a big difference – and these areas may be the canaries of the coal mine.
The biggest hotspot was the northwest Atlantic, where anthropogenic carbon is responsible for 40 to 100 percent of the calcium carbonate in solution. The researchers wrote that there were other small hot spots, in the Indian Ocean and in the South Atlantic, where generous carbon deposits and fast bottom currents accelerate the flow. dissolution rate.
The west of the North Atlantic is where the oceanic layer without calcium carbonate rose to 300 meters. This depth, called compensation depth of calcite, occurs where the rain of calcium carbonate from dead animals is essentially canceled out by the acidity of the oceans. Below this line, there is no accumulation of calcium carbonate.
The increase in depth indicates that, now that there is more carbon in the ocean, dissolution reactions occur more rapidly and at lower depths. This line has evolved over millennia with natural variations in the atmospheric composition of the Earth. Scientists do not yet know what this alteration of the deep sea will mean for the creatures that live there, but future geologists will be able to see man-made climate change in the rocks eventually formed by the seabed current. Some current scholars have already referred to this era as Anthropocene, defining it as the moment when human activities began to dominate the environment.
"The chemical burning of previously deposited carbonate-rich sediments has already begun and will intensify and spread over large areas of the seabed over the next decades and centuries, thus altering the geological record. from the deep sea, "wrote Key and his colleagues. "Deep-sea benthic [bottom] the environment, which covers about 60% of our planet, has indeed entered the Anthropocene ".
Originally published on Science live.
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